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Oceanic Engineering, IEEE Journal of

Issue 2 • Date Apr 1993

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Displaying Results 1 - 9 of 9
  • Modeling bistatic bottom scattering strength including a forward scatter lobe

    Publication Year: 1993 , Page(s): 100 - 107
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    An upgrade to bistatic scattering strength modelling that is based on the authors' current understanding of bottom topographic scattering with an emphasis on modeling the `forward lobe' where Lambert's law fails quite significantly is reported. Low-frequency bottom scatter modeling is reviewed with particular emphasis on the issues of the forward scattered lobe. A specific model (a modified version of BISSM) is proposed, and the model's advantages and limitations are discussed. The requirement for certain high-resolution geomorphic data needed to support the model is discussed. Like the original BISSM, the version does not modify the accepted form for diffuse scattering, but it does modify the form of the forward lobe View full abstract»

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  • Sidescan sonar image processing techniques

    Publication Year: 1993 , Page(s): 108 - 122
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2032 KB)  

    A four-step processing sequence is described to produce image mosaics from the various segments of a sidescanned acoustic imaging survey of a given seafloor area. Starting with data consisting for each ping of acoustic backscatter levels versus horizontal range across-track, median prefiltering is used first to reduce the influence of outliers on subsequent linear processes. Artifacts that are clearly unrelated to the backscattering properties of the seafloor are then isolated on a ping by ping basis through a spectral analysis that relies on a decomposition using Chebyshev polynomials to filter the low spatial frequency components of the image. Contrast enhancement is then achieved through an original implementation of the classical gray level histogram equalization technique by balancing local versus global histogram contributions. Pixels are mapped on a geographic grid taking due account of the geometry of the measurement and of the spacing between pings to minimize along-track smearing of features. Examples of results obtained with these processing techniques are given for SeaMARC II data recorded during a complete survey of Fieberling Guyot (32°.5 N, 128° W) View full abstract»

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  • A methodology for acoustic seafloor classification

    Publication Year: 1993 , Page(s): 81 - 86
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    A seafloor classification methodology, based on a parameterization of the reverberation probability density function in conjunction with neural network classifiers, is evaluated through computer simulations. Different seafloor provides are represented by a number of scatterer distributions exhibiting various degrees of departure from the nominal Poisson distribution. Using a computer simulation program, these distributions were insonified at different spatial scales by varying the transmitted pulse length. The statistical signature obtained consists of reverberation kurtosis estimates as a function of pulse length. Two neural network classifiers are presented with the task of discriminating among the various scatterer distributions based on obtained acoustic signatures. The results indicate that this approach offers considerable promise for practical, realizable solutions to the problem of remote seafloor classification View full abstract»

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  • A nearly unbiased inherently stable bearings-only tracker

    Publication Year: 1993 , Page(s): 138 - 141
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    A pseudolinear estimator for bearings only tracking is presented. It is demonstrated through calculations and simulations that it has a performance close to the computationally far more complex maximum-likelihood estimator, in contrast to the earlier well-known pseudolinear estimator in Cartesian coordinates. Using the mean time point as the time reference of this estimator is necessary in order to avoid bias View full abstract»

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  • The practical implementation of electronic stabilization for sector scanning sonar displays

    Publication Year: 1993 , Page(s): 123 - 129
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    The natural motion of a ship at sea produces undesirable effects on sonar displays. To overcome this problem some form of stabilization is desirable. A practical sonar display system, which uses image processing techniques to stabilize the displayed sonar image against rotational motion is described. The stabilization method provides the capability of image enhancement as well as improved image interpretation due to an increased area of view and a geometrically correct conversion to polar display. Details of the three processing stages required in the system are provided. These processes are ship motion analysis, image integration, and polar display conversion. Stabilized results are given for simulated ship motion View full abstract»

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  • Range and bearing estimation using polynomial rooting

    Publication Year: 1993 , Page(s): 130 - 137
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    Simultaneous estimation of the range and bearing of near-field emitters usually involves a multidimensional search. The authors examine an alternative algorithm which involves search in the range direction combined with polynomial rooting, which replaces the search in the azimuth direction. The proposed algorithm requires a smaller amount of computation than algorithms based on two-dimensional search. The performance of the algorithm is evaluated by Monte Carlo simulation, and is compared to the Cramer-Rao bound on the bearing/range estimation errors. Formulas for computing the bound are derived View full abstract»

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  • Analysis of finite-duration wide-band frequency sweep signals for ocean tomography

    Publication Year: 1993 , Page(s): 87 - 94
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    A group of amplitude and frequency modulated signals which generate narrow synthesized pulses are described. The pulse-compression properties of these signals should approach those of maximal (M) sequence phase-modulated signals now commonly used in ocean experiments. These amplitude-tapered linear frequency-sweep (chirp) type signals should be accurately reproducible with most acoustic sources since they have controllable limited-bandwidth frequency content and differentiable phase. The Doppler response of the signals is calculated using a wideband approach, where the frequency shift from relative motion is not constant throughout the waveform. The resultant Doppler effect on the matched-filter output is a function of the signal duration. The signals are suitable for use with tunable resonant transducers, and have adequate Doppler response for use with Lagrangian ocean drifters View full abstract»

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  • Reverberation fluctuations from a smooth seafloor

    Publication Year: 1993 , Page(s): 95 - 99
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    High-frequency shallow-water reverberation statistics were measured from a smooth, sandy, featureless seafloor. The reverberation statistics are presented as a function of source frequency (20-180 kHz), grazing angle (30°, 20°, 9.5°), and source beamwidths (1.2°-2.75°). Generally, the reverberation statistics did not follow a Rayleigh fading model. The model dependence of the reverberation statistics exhibited a complex behavior that ranged from near Gaussian to beyond log-normal. The results show that small changes in the source frequency, grazing angles, and beamwidths caused large variations in the model dependence of the reverberation statistics View full abstract»

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  • Fair and Andrews's weighting-based IRWLS algorithms for time-delay estimation in underwater target tracking

    Publication Year: 1993 , Page(s): 142 - 150
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Underwater target tracking relies on a model relating the target states to time-delay and bearing measurements. This furnishes linearized measurement models. Problems arise due to fitting models using the least-squares procedure, whose success may depend on the assumption that the data noise distribution is Gaussian. For many cases of non-Gaussian errors, performance of the least-squares estimators is far from optimal. Robust regression procedures have been proposed to improve the performance of the least-squares procedures for non-Gaussian errors, and to enhance their performance for the Gaussian errors. Filters for time-delay estimation based on the Fair and Andrews's weighting functions of the iteratively reweighted least-squares method are proposed. Computational results are given to illustrate and compare the performances of the two filters as well as that due to ordinary least-squares filters View full abstract»

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Aims & Scope

The IEEE Journal of Oceanic Engineering (ISSN 0364-9059) is published quarterly by the IEEE Oceanic Engineering Society (IEEE OES). The scope of the Journal is the field of interest of the IEEE OES, which encompasses all aspects of science, engineering, and technology that address research, development, and operations pertaining to all bodies of water. This includes the creation of new capabilities and technologies from concept design through prototypes, testing, and operational systems to sense, explore, understand, develop, use, and responsibly manage natural resources.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
N. Ross Chapman
School of Earth & Ocean Sciences
University of Victoria
3800 Finnerty Road
Victoria, BC V8P 5C2 Canada
chapman@uvic.ca